GROWTH OF LISTERIA-MONOCYTOGENES AT 21-DEGREES-C IN BIOFILMS WITH MICROORGANISMS ISOLATED FROM MEAT AND DAIRY PROCESSING ENVIRONMENTS

Listeria monocytogenes accumulated in multispecies biofilms grown on s tainless steel at 21-degrees-C over a period of 8 to 10 d. Two dilutio ns of tryptic soy broth were used as growth media. Out of eight compet itive cultures tested, six reduced accumulation of L. monocytogenes in biofilm at one or both of the nutrient levels studied. However, none of the competitive cultures were able to eliminate L. monocytogenes fr om the biofilm. A Flavobacterium isolate stimulated accumulation of L. monocytogenes in biofilm at both nutrient levels. The effect of nutri ent level on the accumulation of L. monocytogenes was dependent on the type of competitive culture used to produce the biofilm.